Changes In Glucose Utilization Research Articles

Fasting and Glucose Metabolism Differentially Impact Peripheral Inflammation in Human Type 2 Diabetes.

Cytokines produced by peripheral T-helper 1/17 cells disproportionately contribute to the inflammation (i.e., metaflammation) that fuels type 2 diabetes (T2D) pathogenesis. Shifts in the nutrient milieu could influence inflammation through changes in T-cell metabolism. We aimed to determine whether changes in glucose utilization alter cytokine profiles in T2D. Peripheral blood mononuclear cells (PBMCs), CD4+ T-cells, and CD4+CD25- T-effector (Teff) cells were isolated from age-matched humans classified by glycemic control and BMI. Cytokines secreted by CD3/CD28-stimulated PBMCs and Teff were measured in supernatants with multiplex cytokine assays and a FLEXMAP-3D. Metabolic activity of stimulated CD4+ T-cells was measured by a Seahorse XFe96 analyzer. In this study, we demonstrated that T-cell stimulated PBMCs from non-fasted people with T2D produced higher amounts of cytokines compared to fasting. Although dysglycemia characterizes T2D, cytokine production by PBMCs or CD4+ T-cells in T2D was unaltered by hyperglycemic media. Moreover, pharmacological suppression of mitochondrial glucose oxidation did not change T-cell metabolism in T2D, yet enhanced cytokine competency. In conclusion, fasting and glucose metabolism differentially impact peripheral inflammation in human T2D, suggesting that glucose, along with fatty acid metabolites per our previous work, partner to regulate metaflammation. These data expose a major disconnect in the use of glycemic control drugs to target T2D-associated metaflammation.

Impact of Normal and Overweight Pregnancy in GLUT4 and Glucose-Dependent Vascular Contractility

Introduction: Obesity during pregnancy can contribute to hypertensive complications through changes in glucose utilization. We investigated the impact of vascular glucose uptake, GLUT4 density, and endothelium on agonist-induced vasoconstriction in the aortas of overweight pregnant rats. Methods: Isolated aortic rings with or without endothelium from pregnant or nonpregnant rats fed a standard (SD) or hypercaloric diet (HD) were contracted with phenylephrine or serotonin (10−9 to 10−4M) using standard (11 mm) or without (0 mm) glucose Krebs solution. GLUT4 density in the aortas was measured using the en face method. Results: Aortas from overweight pregnant animals (PHD) showed increased Phe-induced vasoconstriction (p < 0.05 vs. pregnant standard diet [PSD]), which was endothelium-independent. The contraction decreased significantly in the absence of glucose. In contrast, vessels from pregnant SD rats maintained their contraction in glucose-free Krebs solution. 5-HT increases PHD aortic contraction only in the absence of glucose. The fetal aortas from PHD mothers showed blunted vasoconstriction. Overweight significantly reduced GLUT4 expression in maternal and fetal aortas (p < 0.05 vs. PSD). Conclusions: Aortic contractility is independent of glucose uptake during healthy pregnancy. In contrast, overweight pregnancy increases contractility. This increase depends directly on smooth muscle glucose uptake and inversely on GLUT-4 density. The increased contraction observed in the vasculature of overweight mothers was inverted in the fetal aortas.

Clozapine induces astrocyte-dependent FDG-PET hypometabolism.

Advances in functional imaging allowed us to visualize brain glucose metabolism in vivo and non-invasively with [18F]fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) imaging. In the past decades, FDG-PET has been instrumental in the understanding of brain function in health and disease. The source of the FDG-PET signal has been attributed to neuronal uptake, with hypometabolism being considered as a direct index of neuronal dysfunction or death. However, other brain cells are also metabolically active, including astrocytes. Based on the astrocyte-neuron lactate shuttle hypothesis, the activation of the glutamate transporter 1 (GLT-1) acts as a trigger for glucose uptake by astrocytes. With this in mind, we investigated glucose utilization changes after pharmacologically downregulating GLT-1 with clozapine (CLO), an anti-psychotic drug. Adult male Wistar rats (control, n = 14; CLO, n = 12) received CLO (25/35mgkg-1) for 6weeks. CLO effects were evaluated in vivo with FDG-PET and cortical tissue was used to evaluate glutamate uptake and GLT-1 and GLAST levels. CLO treatment effects were also assessed in cortical astrocyte cultures (glucose and glutamate uptake, GLT-1 and GLAST levels) and in cortical neuronal cultures (glucose uptake). CLO markedly reduced in vivo brain glucose metabolism in several brain areas, especially in the cortex. Ex vivo analyses demonstrated decreased cortical glutamate transport along with GLT-1 mRNA and protein downregulation. In astrocyte cultures, CLO decreased GLT-1 density as well as glutamate and glucose uptake. By contrast, in cortical neuronal cultures, CLO did not affect glucose uptake. This work provides in vivo demonstration that GLT-1 downregulation induces astrocyte-dependent cortical FDG-PET hypometabolism-mimicking the hypometabolic signature seen in people developing dementia-and adds further evidence that astrocytes are key contributors of the FDG-PET signal.

Role of Estrogen and Its Receptors in Adipose Tissue Glucose Metabolism in Pre- and Postmenopausal Women

ContextReduced estrogen levels in postmenopausal women predispose them to metabolic side effects, including insulin resistance and type 2 diabetes; however, the cellular mechanisms are not well understood.ObjectiveThis work aimed to study the expression of estrogen receptors in adipose tissue from pre- and postmenopausal women and the effects of estradiol (E2) on glucose uptake of adipocytes.MethodsSubcutaneous (SAT) and visceral adipose tissue (VAT) obtained from pre- and postmenopausal women (19-51 and 46-75 years old, respectively) were used to measure gene expression of ESR1 and ESR2. SAT tissue was incubated with E2, and glucose uptake and estrogen receptor levels were measured. Polymorphisms in ESR1 and ESR2 were addressed in public databases to identify single nucleotide polymorphisms associated with metabolic traits.Results ESR2 expression was lower in pre- vs postmenopausal women, corresponding to lower ESR1:ESR2 gene expression ratio in postmenopausal women. In premenopausal women, the expression of ESR1 was higher in VAT than in SAT. In both pre- and postmenopausal women, ESR2 expression was lower in VAT than in SAT. In late, but not pre- or early postmenopausal women, E2 reduced glucose uptake and GLUT4 protein and increased expression of ESR2. ESR1 polymorphisms were associated with weight, body fat distribution, and total cholesterol, and ESR2 polymorphisms were associated with total cholesterol and triglyceride levels and with body fat percentage.ConclusionE2 inhibits glucose utilization in human adipocytes in late postmenopausal women. Changes in glucose utilization over time since menopause may be explained by a lower ESR1:ESR2 ratio. This can have clinical implications on the timing of estrogen treatment in postmenopausal women.

Adaptive Thermogenesis Driving Catch-Up Fat Is Associated With Increased Muscle Type 3 and Decreased Hepatic Type 1 Iodothyronine Deiodinase Activities: A Functional and Proteomic Study.

Refeeding after caloric restriction induces weight regain and a disproportionate recovering of fat mass rather than lean mass (catch-up fat) that, in humans, associates with higher risks to develop chronic dysmetabolism. Studies in a well-established rat model of semistarvation-refeeding have reported that catch-up fat associates with hyperinsulinemia, glucose redistribution from skeletal muscle to white adipose tissue and suppressed adaptive thermogenesis sustaining a high efficiency for fat deposition. The skeletal muscle of catch-up fat animals exhibits reduced insulin-stimulated glucose utilization, mitochondrial dysfunction, delayed in vivo contraction-relaxation kinetics, increased proportion of slow fibers and altered local thyroid hormone metabolism, with suggestions of a role for iodothyronine deiodinases. To obtain novel insights into the skeletal muscle response during catch-up fat in this rat model, the functional proteomes of tibialis anterior and soleus muscles, harvested after 2 weeks of caloric restriction and 1 week of refeeding, were studied. Furthermore, to assess the implication of thyroid hormone metabolism in catch-up fat, circulatory thyroid hormones as well as liver type 1 (D1) and liver and skeletal muscle type 3 (D3) iodothyronine deiodinase activities were evaluated. The proteomic profiling of both skeletal muscles indicated catch-up fat-induced alterations, reflecting metabolic and contractile adjustments in soleus muscle and changes in glucose utilization and oxidative stress in tibialis anterior muscle. In response to caloric restriction, D3 activity increased in both liver and skeletal muscle, and persisted only in skeletal muscle upon refeeding. In parallel, liver D1 activity decreased during caloric restriction, and persisted during catch-up fat at a time-point when circulating levels of T4, T3 and rT3 were all restored to those of controls. Thus, during catch-up fat, a local hypothyroidism may occur in liver and skeletal muscle despite systemic euthyroidism. The resulting reduced tissue thyroid hormone bioavailability, likely D1- and D3-dependent in liver and skeletal muscle, respectively, may be part of the adaptive thermogenesis sustaining catch-up fat. These results open new perspectives in understanding the metabolic processes associated with the high efficiency of body fat recovery after caloric restriction, revealing new implications for iodothyronine deiodinases as putative biological brakes contributing in suppressed thermogenesis driving catch-up fat during weight regain.

In vitro Characterization of Insulin−Producing β-Cell Spheroids

Over the years, immortalized rodent β-cell lines such as RIN, HIT, MIN, βTC, and INS-1 have been used to investigate pancreatic β-cell physiology using conventional two-dimensional (2D) culture techniques. However, physical and physiological limitations inherent to 2D cell culture necessitates confirmatory follow up studies using sentient animals. Three-dimensional (3D) culture models are gaining popularity for their recapitulation of key features of in vivo organ physiology, and thus could pose as potential surrogates for animal experiments. In this study, we aimed to develop and characterize a rat insulinoma INS-1 3D spheroid model to compare with 2D monolayers of the same cell line. Ultrastructural verification was done by transmission electron microscopy and toluidine blue staining, which showed that both 2D monolayers and 3D spheroids contained highly granulated cells with ultrastructural features synonymous with mature pancreatic β-cells, with increased prominence of these features observed in 3D spheroids. Viability, as assessed by cellular ATP quantification, size profiling and glucose utilization, showed that our spheroids remained viable for the experimental period of 30 days, compared to the limiting 5-day passage period of INS-1 monolayers. In fact, increasing ATP content together with spheroid size was observed over time, without adverse changes in glucose utilization. Additionally, β-cell function, assessed by determining insulin and amylin secretion, showed that the 3D spheroids retained glucose sensing and insulin secretory capability, that was more acute when compared to 2D monolayer cultures. Thus, we were able to successfully demonstrate that our in vitro INS-1 β-cell 3D spheroid model exhibits in vivo tissue-like structural features with extended viability and lifespan. This offers enhanced predictive capacity of the model in the study of metabolic disease, β-cell pathophysiology and the potential treatment thereof.

Mechanisms Underlying Type 2 Diabetes Remission After Metabolic Surgery.

Type 2 diabetes prevalence is increasing dramatically worldwide. Metabolic surgery is the most effective treatment for selected patients with diabetes and/or obesity. When compared to intensive medical therapy and lifestyle intervention, metabolic surgery has shown superiority in achieving glycemic improvement, reducing number of medications and cardiovascular risk factors, which translates in long-term benefits on cardiovascular morbidity and mortality. The mechanisms underlying diabetes improvement after metabolic surgery have not yet been clearly understood but englobe a complex interaction among improvements in beta cell function and insulin secretion, insulin sensitivity, intestinal gluconeogenesis, changes in glucose utilization, and absorption by the gut and changes in the secretory pattern and morphology of adipose tissue. These are achieved through different mediators which include an enhancement in gut hormones release, especially, glucagon-like peptide 1, changes in bile acids circulation, gut microbiome, and glucose transporters expression. Therefore, this review aims to provide a comprehensive appraisal of what is known so far to better understand the mechanisms through which metabolic surgery improves glycemic control facilitating future research in the field.

Developmental Aspects of Glucose and Calcium Availability on the Persistence of Memory Function Over the Lifespan.

An important aspect concerning the underlying nature of memory function is an understanding of how memories are acquired and lost. The stability, and ultimate demise, of memory over the lifespan of an organism remains a critical topic in determining the neurobiological mechanisms that mediate memory representations. This has important implications for the elucidation and treatment of neurodegenerative diseases such as Alzheimer’s disease (AD). One important question in the context of preserving functional plasticity over the lifespan is the determination of the neurobiological structural and functional changes that contribute to the formation of memory during the juvenile time frame that might provide protection against later memory dysfunction by promoting the establishment of redundant neural pathways. The main question being, if memory formation during the juvenile period does strengthen and preserve memory stability over the lifespan, what are the neurobiological structural or functional substrates that mediate this effect? One neural attribute whose function may be altered with early life experience and provide a mechanism to preserve memory through the lifespan is glucose transport-linked calcium (Ca2+) buffering. Because peak increases in glucose utilization overlap with a timeframe during which spatial training can enhance later memory processing, it might be the case that learning-associated changes in glucose utilization would provide an important neural functional change to preserve memory function throughout the lifespan. The glucose transporters are proteins that are reduced in AD pathology and there is evidence that glucose reductions can impair Ca2+ buffering. In the absence of an appropriate supply of ATP, provided via glucose transport and glycolysis, Ca2+ levels can rise leading to neural vulnerability with ensuing pathological outcomes. In this review, we explore the hypothesis that enhancing glucose utilization with spatial training during the preadolescent period will provide a functional enhancement that regulates glucose-dependent Ca2+ signaling during aging or neurodegeneration and provide essential neural resources to preserve functional plasticity and memory function.

Dysregulated Glucose Metabolism as a Therapeutic Target to Reduce Post-traumatic Epilepsy.

Traumatic brain injury (TBI) is a significant cause of disability worldwide and can lead to post-traumatic epilepsy. Multiple molecular, cellular, and network pathologies occur following injury which may contribute to epileptogenesis. Efforts to identify mechanisms of disease progression and biomarkers which predict clinical outcomes have focused heavily on metabolic changes. Advances in imaging approaches, combined with well-established biochemical methodologies, have revealed a complex landscape of metabolic changes that occur acutely after TBI and then evolve in the days to weeks after. Based on this rich clinical and preclinical data, combined with the success of metabolic therapies like the ketogenic diet in treating epilepsy, interest has grown in determining whether manipulating metabolic activity following TBI may have therapeutic value to prevent post-traumatic epileptogenesis. Here, we focus on changes in glucose utilization and glycolytic activity in the brain following TBI and during seizures. We review relevant literature and outline potential paths forward to utilize glycolytic inhibitors as a disease-modifying therapy for post-traumatic epilepsy.

Imaging Brain Metabolism in the Newborn.

In this review, we discuss molecular brain imaging studies using positron emission tomography (PET) with 2-deoxy-2(18F)fluoro-d-glucose (FDG) in human newborns and infants, and illustrate how this technology can be applied to probe the neuropathophysiology of neonatal neurologic disorders. PET studies have been difficult to perform in sick babies because of patient transportation issues and suboptimal spatial resolution. With approval from the FDA and the institutional review board, we modified and installed the Focus 220 animal microPET scanner (Concorde Microsystems, Knoxville, TN) directly in our neonatal intensive care unit in Children's Hospital of Michigan and verified the high spatial resolution (<2 mm full-width-at-half-maximum) of this microPET. The neonatal pattern of glucose metabolism is very consistent, with the highest degree of activity in primary sensory and motor cortex, medial temporal region, thalamus, brain stem, and cerebellar vermis. Prior studies have shown that increases of glucose utilization are seen by 2 to 3 months in the parietal, temporal, cingulate, and primary visual cortex; basal ganglia; and cerebellar hemispheres. Between 6 and 8 months, lateral and inferior frontal cortex becomes more functionally active and, eventually, between 8 and 12 months, the dorsal and medial frontal regions also show a maturational increase. These findings are consistent with the physical, behavioral, and cognitive maturation of the infant. At birth, metabolic rates of glucose utilization in cortex are about 30% lower than in adults but rapidly rise such that, by 3 years, the cerebral cortical rates exceed adult rates by more than 2-fold. At around puberty, the rates for cerebral cortex begin to decline and gradually reach adult values by 16-18 years. These nonlinear changes of glucose utilization indirectly reflect programed periods of synaptic proliferation and pruning in the brain. Positron emission tomographic (PET) imaging of GABAA receptors (using 11C-flumazenil) in newborns also show a pattern very different from adults, with high binding in amygdala-hippocampus, sensory-motor cortex, thalamus, brain stem, and basal ganglia, in that order. We speculate that the early development of amygdala/hippocampus prepares the baby for bonding, attachment, and memory, and the deprivation of such experiences during a sensitive period results in malfunction of these networks and psychopathology, as has been shown in studies on severely socioemotionally deprived children. Recently developed hybrid PET/magnetic resonance (MR) scanners allow the simultaneous acquisition of PET and MR data sets with advanced applications. These devices are particularly advantageous for scanning babies and infants because of the high spatial resolution, automated coregistration of anatomical and functional images and, in the case of need for sedation, maximal data acquired in 1 session.

Modeling gold nanoparticle biodistribution after arterial infusion into perfused tissue: effects of surface coating, size and protein corona

A detailed understanding of the factors governing nanomaterial biodistribution is needed to rationally design safe nanomedicines. This research details the pharmacokinetics of gold nanoparticle (AuNP) biodistribution after arterial infusion of 40 or 80 nm AuNP (1 μg/ml) into the isolated perfused porcine skin flap (IPPSF). AuNP had surface coatings consisting of neutral polyethylene glycol (PEG), anionic lipoic acid (LA), or cationic branched polyethylenimine (BPEI). Effect of a porcine plasma corona (PPC) on 40 nm BPEI and PEG-AuNP were assessed in the IPPSF. Au concentrations were determined by ICP/MS and arterial to venous concentration-time profiles were analyzed over 8 hr (4 hr infusion, 4 hr washout) using a two-compartment pharmacokinetic model. IPPSF viability and vascular function were assessed by change in glucose utilization, vascular resistance, or weight gain after perfusion. All AuNP demonstrated some degree of AuNP arterial extraction and skin flap retention, as well as enhanced kinetic parameters of tissue uptake; with BPEI-AuNP consistently having the greatest biodistribution even with a PPC. Toxicological effects were not detected. Transmission electron microscopy confirmed intracellular uptake of AuNP. These studies paralleled previous in vitro cell culture studies using the same AuNP in human endothelial and renal proximal tubule cells, hepatocytes, keratinocytes, showing BPEI-AuNP having the greatest uptake, although the presence of a PPC did not reduce IPPSF biodistribution as in the cell culture studies. These findings clearly indicate arterial to the venous extraction of AuNP after infusion with the magnitude of extraction being greatest with the BPEI surface coating and provide data and model structure necessary to construct the whole body physiologically based pharmacokinetic models capable of utilizing available in vitro data.

GLUCOSE METABOLISM AS A THERAPEUTIC TARGET IN ALZHEIMER’S DISEASE

Reduced brain glucose metabolism is a consistent feature of Alzheimer's disease (AD), and predicts progression from amnestic mild cognitive impairment (aMCI) to AD dementia. Greater decreases in F18fluorodeoxyglucose uptake with positron emission tomography (FDG-PET) correlate with greater cognitive impairment along the continuum from normal cognitive status to aMCI to AD dementia. In spite of the tight linkage of glucose metabolism to brain function and the decline in AD, only a very limited number of studies have tried to understand why glucose utilization is diminished or tried to reverse this AD-related deficit. Thiamine-dependent enzymes are critical components of glucose metabolism and are reduced in brains of AD patients. Increasing thiamine in humans or animals increases glucose utilization, improves brain metabolism and cognition, including memory. The most effective way to increase blood and brain thiamine is with benfotiamine because of superior pharmacokinetics. Our aim is to test the effect of administering benfotiamine on brain glucose metabolism (FDG-PET) and clinical impact as measured by changes in Assessment Scale-Cognitive subscale (ADAS-Cog) over time in patients with aMCI or AD. A randomized, double-blind, placebo-controlled clinical trial with benfotiamine in patients with aMCI or mild AD was initiated. The primary objective is to determine whether increasing thiamine availability with benfotiamine can slow cognitive decline compared to placebo, as measured by a change in the ADAS Cog score over the twelve-month trial. The secondary objective is to test whether benfotiamine will slow the decline in glucose utilization in patients as measured by FDG-PET. Using blocked, stratified randomization, 76 patients will be assigned to the treatment or placebo group. Stratification is based on Mini Mental Status Exam score (>21) to better understand if treatment responses differ according to initial cognitive impairment. Of the 464 patients screened, 45 patients have been enrolled. Patient characteristics will be detailed in the poster. The trial will determine whether benfotiamine provides clinical or underlying biological benefit for aMCI/AD patients and if this correlates with changes in glucose utilization.

Diabetic db/db mice do not develop heart failure upon pressure overload: a longitudinal in vivo PET, MRI, and MRS study on cardiac metabolic, structural, and functional adaptations.

Heart failure is associated with altered myocardial substrate metabolism and impaired cardiac energetics. Comorbidities like diabetes may influence the metabolic adaptations during heart failure development. We quantified to what extent changes in substrate preference, lipid accumulation, and energy status predict the longitudinal development of hypertrophy and failure in the non-diabetic and the diabetic heart. Transverse aortic constriction (TAC) was performed in non-diabetic (db/+) and diabetic (db/db) mice to induce pressure overload. Magnetic resonance imaging, 31P magnetic resonance spectroscopy (MRS), 1H MRS, and 18F-fluorodeoxyglucose-positron emission tomography (PET) were applied to measure cardiac function, energy status, lipid content, and glucose uptake, respectively. In vivo measurements were complemented with ex vivo techniques of high-resolution respirometry, proteomics, and western blotting to elucidate the underlying molecular pathways. In non-diabetic mice, TAC induced progressive cardiac hypertrophy and dysfunction, which correlated with increased protein kinase D-1 (PKD1) phosphorylation and increased glucose uptake. These changes in glucose utilization preceded a reduction in cardiac energy status. At baseline, compared with non-diabetic mice, diabetic mice showed normal cardiac function, higher lipid content and mitochondrial capacity for fatty acid oxidation, and lower PKD1 phosphorylation, glucose uptake, and energetics. Interestingly, TAC affected cardiac function only mildly in diabetic mice, which was accompanied by normalization of phosphorylated PKD1, glucose uptake, and cardiac energy status. The cardiac metabolic adaptations in diabetic mice seem to prevent the heart from failing upon pressure overload, suggesting that restoring the balance between glucose and fatty acid utilization is beneficial for cardiac function.

Abstract PR03: GLUT1 is required for induction of mammary tumorigenesis by activated ErbB2/HER2/Neu

Abstract Alterations in tumor cell metabolism have been investigated for decades, and include changes in glucose utilization, as well as changes in mitochondrial and fatty acid metabolism; however, it is unclear at what point during the process of tumorigenesis these metabolic changes occur. We hypothesized that elevated glucose uptake represents the first metabolic adaptation to transformation, and thus may be a target for the prevention of breast cancer. The GLUT1 transporter is expressed in breast cancer cells and is responsible for the majority of their glucose uptake. Not surprisingly, breast cancer patients with high levels of GLUT1 have a poorer clinical outcome than those with lower levels, likely due to the association between glucose uptake and high tumor grade. We previously showed that the reduction of GLUT1 in established tumor cells resulted in a 50% decrease in glucose consumption and lactate generation. There was a corresponding decrease in proliferation in both two and three-dimensional culture, and in tumor growth in immunodeficient mice. Mammary epithelial cells from GLUT1fl/fl mice were transformed using polyoma middle tumor antigen (PyMT), and GLUT1 excised using Cre recombinase. Cells expressing GLUT1 were tumorigenic in immunodeficient mice, while cells lacking GLUT1 were not tumorigenic. This suggests that in mammary epithelial cells transformed in vitro, loss of GLUT1 was sufficient to prevent tumor outgrowths when injected into the mammary fat pad of nude mice. This indicates that GLUT1 and by extension glucose, are critical at an early stage of mammary tumorigenesis. To test the hypothesis that elevated glucose uptake is required very early in the process of tumor formation, we crossed the MMTV-NIC (NIC) mice, which contain activated NeuNT, an internal ribosome entry site (IRES), and Cre recombinase, to mice bearing floxed alleles of GLUT1, and monitored tumor development. All of the control MMTV-NIC mice developed tumors in less than 200 days. In contrast, none of the NIC-GLUT1fl/fl mice developed mammary tumors even after eighteen months. We anticipated that loss of one allele of GLUT1 would significantly delay mammary tumorigenesis; however, we did not observe any tumors in these mice, even at eighteen months of age. Tumors that formed in the NIC mice were typical Neu-dependent tumors observed in similar transgenic mice with a high proliferative index (38% by Ki67 staining), and there was evidence of preneoplastic lesions in the non tumor-bearing mammary glands. Small Cre-positive lesions were also positive for GLUT1 indicating GLUT1 expression increases very early in Neu-mediated tumorigenesis. The mammary ductal tree developed normally in NIC-Glut1fl/fl and NIC-Glut1fl/+ mice. Mammary glands from mice lacking one allele of GLUT1 had increased epithelial content and higher proliferative index, compared to mice lacking both Glut1 alleles; however, no palpable tumors ever formed in either group. These results suggest that loss of a single allele of GLUT1 is sufficient to suppress Neu-induced mammary tumorigenesis and that there is an absolute requirement for GLUT1 at the earliest stages of tumorigenesis. Citation Format: Elizabeth A. Wellberg, Angelo D'Allessandro, Andrew S. Lewis, Kristina Terrell, E. Dale Abel, William A. Muller, Kirk A. Hansen, Steven M. Anderson. GLUT1 is required for induction of mammary tumorigenesis by activated ErbB2/HER2/Neu. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr PR03.

Biochemical, Metabolic, and Behavioral Characteristics of Immature Chronic Hyperphenylalanemic Rats.

Phenylketonuria and hyperphenylalanemia are inborn errors in metabolism of phenylalanine arising from defects in steps to convert phenylalanine to tyrosine. Phe accumulation causes severe mental retardation that can be prevented by timely identification of affected individuals and their placement on a Phe-restricted diet. In spite of many studies in patients and animal models, the basis for acquisition of mental retardation during the critical period of brain development is not adequately understood. All animal models for human disease have advantages and limitations, and characteristics common to different models are most likely to correspond to the disorder. This study established similar levels of Phe exposure in developing rats between 3 and 16 days of age using three models to produce chronic hyperphenylalanemia, and identified changes in brain amino acid levels common to all models that persist for ~16 h of each day. In a representative model, local rates of glucose utilization (CMRglc) were determined at 25-27 days of age, and only selective changes that appeared to depend on Phe exposure were observed. CMRglc was reduced in frontal cortex and thalamus and increased in hippocampus and globus pallidus. Behavioral testing to evaluate neuromuscular competence revealed poor performance in chronically-hyperphenylalanemic rats that persisted for at least 3 weeks after cessation of Phe injections and did not occur with mild or acute hyperphenylalanemia. Thus, the abnormal amino acid environment, including hyperglycinemia, in developing rat brain is associated with selective regional changes in glucose utilization and behavioral abnormalities that are not readily reversed after they are acquired.

Simultaneous functional imaging using fPET and fMRI.

Brain mapping of task-associated changes in metabolism with PET has been accomplished by subtracting scans acquired during two distinct static states. We have demonstrated that PET can provide truly dynamic information on cerebral energy metabolism using constant infusion of FDG and multiple stimuli in a single experiment. We demonstrate here that the functional PET (fPET-FDG) method accomplished simultaneously with fMRI, can enable the first direct comparisons in time, space and magnitude of hemodynamics and oxygen and glucose consumption. The imaging studies were performed on a 3T Tim-Trio MR scanner modified to support an MR-compatible BrainPET insert. Ten healthy subjects were included. The total PET acquisition and infusion time was 90 minutes. We did 3 blocks of right hand fingers tapping for 10 minutes at 30, 50 and 70 minutes after the beginning of the PET acquisition. ASL and BOLD imaging were acquired simultaneously during the motor paradigm. Changes in glucose utilization are easily observed as changes in the TAC slope of the PET data (FDG utilization rate) and in the derivative signal during motor stimuli in the activated voxels. PET and MRI (ASL, and BOLD) activations are largely colocalized but with very different statistical significance and temporal dynamic, especially in the ipsilateral side of the stimuli. This study demonstrated that motor activation can be measured dynamically during a single FDG PET scan. The complementary nature of fPET-FDG to fMRI capitalizes on the emerging technology of hybrid MR-PET scanners. fPET-FDG, combined with quantitative fMRI methods, allow us to simultaneously measure dynamic changes in glucose utilization and hemodynamic, addressing vital questions about neurovascular coupling.

Improving Cerebral Blood Flow Through Liposomal Delivery of Angiogenic Peptides: Potential of ¹⁸F-FDG PET Imaging in Ischemic Stroke Treatment.

Strategies to promote angiogenesis can benefit cerebral ischemia. We determined whether liposomal delivery of angiogenic peptides with a known biologic activity of vascular endothelial growth factor benefitted cerebral ischemia. Also, the study examined the potential of (18)F-FDG PET imaging in ischemic stroke treatment. Male Sprague-Dawley rats (n = 40) underwent 40 min of middle cerebral artery occlusion. After 15 min of reperfusion, the rats (n = 10) received angiogenic peptides incorporated into liposomes. Animals receiving phosphate-buffered solution or liposomes without peptides served as controls. One week later, (18)F-FDG PET imaging was performed to examine regional changes in glucose utilization in response to the angiogenic therapy. The following day, (99m)Tc-hexamethylpropyleneamine oxime autoradiography was performed to determine changes in cerebral perfusion after angiogenic therapy. Corresponding changes in angiogenic markers, including von Willebrand factor and angiopoietin-1 and -2, were determined by immunostaining and polymerase chain reaction analysis, respectively. A 40-min period of middle cerebral artery occlusion decreased blood perfusion in the ipsilateral ischemic cortex of the brain, compared with that in the contralateral cortex, as measured by (99m)Tc-hexamethylpropyleneamine oxime autoradiography. Liposomal delivery of angiogenic peptides to the ischemic hemisphere of the brain attenuated the cerebral perfusion defect compared with controls. Similarly, vascular density evidenced by von Willebrand factor-positive staining was increased in response to angiogenic therapy, compared with that of controls. This increase was accompanied by an early increase in angiopoietin-2 expression, a gene participating in angiogenesis. (18)F-FDG PET imaging measured at 7 d after treatment revealed that liposomal delivery of angiogenic peptides facilitated glucose utilization in the ipsilateral ischemic cortex of the brain, compared with that in the controls. Furthermore, the change in regional glucose utilization was correlated with the extent of improvement in cerebral perfusion (r = 0.742, P = 0.035). Liposomal delivery of angiogenic peptides benefits cerebral ischemia. (18)F-FDG PET imaging holds promise as an indicator of the effectiveness of angiogenic therapy in cerebral ischemia.

Dynamic functional imaging of brain glucose utilization using fPET-FDG

Glucose is the principal source of energy for the brain and yet the dynamic response of glucose utilization to changes in brain activity is still not fully understood. Positron emission tomography (PET) allows quantitative measurement of glucose metabolism using 2-[18F]-fluorodeoxyglucose (FDG). However, FDG PET in its current form provides an integral (or average) of glucose consumption over tens of minutes and lacks the temporal information to capture physiological alterations associated with changes in brain activity induced by tasks or drug challenges. Traditionally, changes in glucose utilization are inferred by comparing two separate scans, which significantly limits the utility of the method. We report a novel method to track changes in FDG metabolism dynamically, with higher temporal resolution than exists to date and within a single session. Using a constant infusion of FDG, we demonstrate that our technique (termed fPET-FDG) can be used in an analysis pipeline similar to fMRI to define within-session differential metabolic responses. We use visual stimulation to demonstrate the feasibility of this method. This new method has a great potential to be used in research protocols and clinical settings since fPET-FDG imaging can be performed with most PET scanners and data acquisition and analysis are straightforward. fPET-FDG is a highly complementary technique to MRI and provides a rich new way to observe functional changes in brain metabolism.

Comparison of mechanisms underlying changes in glucose utilization in fasted rats anesthetized with propofol or sevoflurane: Hyperinsulinemia is exaggerated by propofol with concomitant insulin resistance induced by an acute lipid load.

The effects of anesthesia with sevoflurane and with propofol on glucose utilization in rats were investigated. Sevoflurane significantly impairs glucose utilization whereas propofol does not. Both insulin secretion and sensitivity affect glucose utilization. Propofol is hydrophobic, and anesthesia with this agent is always accompanied by an acute lipid load, which can exaggerate insulin resistance. The role of the acute lipid load in the effects of anesthesia with sevoflurane and propofol on glucose utilization in fasted rats was investigated. Rats were allocated to groups anesthetized with sevoflurane and infused with physiological saline (group S) or 10% w/v lipid (group SL), or those anesthetized with propofol (group P). Intravenous glucose tolerance tests and insulin tolerance tests were then performed to measure glucose utilization, and blood glucose, plasma insulin, and plasma TNF-α levels were measured. In the intravenous glucose tolerance test, groups SL and P showed significantly higher plasma insulin levels than group S, and group P showed significantly higher plasma insulin levels than group SL. In the insulin tolerance test, groups SL and P showed insulin resistance compared to group S, but no significant difference was observed between groups SL and P. In summary, propofol anesthesia enhances insulin secretion and concomitantly exaggerates insulin resistance, compared with sevoflurane anesthesia. Propofol appears to be the main cause of hyperinsulinemia, and the acute lipid load exaggerates insulin resistance.

Targeting Emotion Circuits with Deep Brain Stimulation in Refractory Anorexia Nervosa

There is an urgent need to develop novel therapies for patients with anorexia nervosa (AN). A condition that is heterogeneous, highly resistant to treatment, and associated with striking rates of morbidity and mortality, few therapeutic advances specifically for AN have been made in the past 150 years. A re-orientation in the last two decades toward neuroscientific explanations for AN offers hope that an increased understanding of the illness' neural roots will lead to better treatments (Kaye et al, 2009). Deep brain stimulation (DBS) is a neurosurgical procedure that targets critical nodes in dysfunctional neural circuits driving pathological behaviors (Lozano and Lipsman, 2013; Mayberg et al, 2005). DBS' efficacy in disorders like Parkinson's Disease has driven its investigation in other circuit-based conditions, including major depression (Lozano and Lipsman, 2013). Several factors led us to consider DBS in refractory AN. First, the primarily limbic structures implicated in the disorder, largely by functional neuroimaging, are consistent with the clinical observations that AN is predominantly a disorder of emotional processing. Further, the ability of DBS to safely and effectively access limbic nodes in mood- and anxiety-related circuits suggested that it could be applied to AN, a disorder marked by high rates of depressed mood and affective dysregulation. The subcallosal cingulate (SCC) has a key role in modulating emotional states and projects cortically, to medial- and orbitofrontal cortex, as well as subcortically to nucleus accumbens. Our group has also shown that SCC neurons participate directly in emotion processing, responding preferentially to affective-laden stimuli and decisions (Lipsman et al, 2013a). The SCC is thus both structurally and functionally integrated into emotion pathways, and its activity linked to disorders of emotion. Our initial experience in a small group of treatment-refractory patients (N=6; average age: 38 years; average illness duration: 18 years) showed DBS to be reasonably safe in AN, and associated with improvements in comorbid mood and anxiety symptoms (Lipsman et al, 2013b). These results were maintained during 6 months of clinical follow-up, with significant reductions in depressed mood and anxiety translating, over time, into increases in BMI (Figure 1). Although time spent on eating- and weight-related preoccupations and rituals did decrease (Lipsman et al, 2013b), we believe the primary effect of DBS was an improved utilization of conventional AN treatment as a result of improved mood and affective regulation. Figure 1 Mean (N=6) percentage changes from baseline, of weight and depression ratings, at each study time point (1 month, 3 months, and 6 months). At 6 months post-DBS, the cohort experienced a mean 12% increase in BMI and a 40% reduction in depression ... The influence of focal stimulation on global cerebral metabolism can be investigated with functional imaging, such as positron emission tomography (PET; Figure 2). PET studies in both AN and depression patients have shown significant network-wide changes in glucose utilization with DBS of the SCC. For example, after 6 months of DBS, both patient groups see significant activity reductions in the SCC and insula, as well as significant activity increases in the parietal lobe (Lipsman et al, 2013b; Mayberg et al, 2005). In AN, this change in parietal activity constitutes an effective reversal of known baseline parietal hypometabolism seen in acutely ill AN patients (Delvenne et al, 1996). These results confirm that although DBS is a focal, targeted therapy, it can influence metabolism in remote regions, and that AN-relevant structures, such as those governing mood, emotion regulation, and body perception, can be modulated by SCC stimulation. Figure 2 Three-dimensional rendering of composite cerebral metabolic changes in six patients who underwent deep brain stimulation of subcallosal cingulum for anorexia nervosa. Red indicates areas of increased activity following 6 months of stimulation compared ... Determining the potential role of DBS in the AN treatment algorithm will await the results of larger, sham-stimulation trials. It is clear, however, that the condition's physical and emotional symptoms are inextricably linked, and novel treatment strategies will need to address both in equal measure, to offer patients hope for a meaningful and enduring recovery.